Nuclear Stress Tests There are three types of Dual Isotope Stress Test: Exercise dual isotope Adenosine dual isotope Dobutamine dual isotope What is a dual isotope or nuclear stress test and what does it show? A dual isotope or nuclear stress test is a diagnostic nuclear imaging study that uses radioactive tracers, called Cardiolite and thallium, to produce images of the heart muscle. When combined with stress, either through exercise or use of a pharmacological agent, the dual isotope scan helps determine if the heart muscle is getting the blood supply it needs. If you are unable to exercise, your doctor may order a pharmacologic stress test, with either adenosine or dobutamine, to simulate exercise and obtain the same information as an exercise stress test. As coronary artery disease (CAD) progresses, the heart muscle may not receive enough blood when under stress (for example, when exercising). This often results in chest pain called angina pectoris. On the other hand, there may be no outward physical signs of the disease. If CAD is limiting blood flow to part of your heart, the dual isotope stress test may be useful in detecting the presence and significance of CAD. What does dual isotope mean? The nuclear stress tests we perform at CVMG are known as “dual isotope” because we use two different radioactive tracers or isotopes to obtain the highest quality information as efficiently and safely as possible. Cardiolite and thallium are the two radioactive isotopes injected through a small IV usually inserted in the arm or wrist. They travel in the bloodstream through the coronary arteries until they are picked up by the heart muscle cells. The areas of the heart that have an adequate blood supply pick up the tracer right away and more completely. Areas that do not have adequate blood supply pick up the tracer very slowly or not at all. The radioactive isotopes give off a small amount of radiation that is detected with a nuclear scanning camera. A computer processes the information and produces the images of the isotopes distributed in the heart. If an area receives less blood than the rest of the heart (because of a blocked or narrowed artery), it will pick up a lower level of radioactivity and will show up as a lighter area, called a "defect." This is how we can tell whether or not there might be a blocked artery in the heart. A dual isotope stress test consists of two parts, rest and stress: Thallium will be administered by injection through your IV while you are at rest, and a special camera will take pictures of your heart. Cardiolite will be administered to you one other time by an IV injection during the stress portion of the test, and additional pictures will be taken of your heart. This allows the doctor to compare the amount of blood flowing through the heart muscle during stress and at rest. The amount of radiation you will be exposed to is comparable to that from an x-ray or computed tomography (CT) scan. The half-life of Cardiolite is approximately 6 hours. This means that half of the dose you are given will decay in 6 hours. The half-life of thallium is longer at approximately 72 hours. This means that half of the dose you are given will decay in 72 hours. You won't feel any different after you are injected with the radioactive isotopes. Most patients experience no side effects. Occasionally patients have a metallic taste in their mouth. How do I prepare for the test? Do not eat or drink for four hours prior to the test, and consume no caffeine for 24 hours prior to the test. The pictures of your heart are clearer when the stomach is not full. If you are diabetic or need to eat/drink with your medication, get special instructions from your doctor. Avoid any strenuous physical activity on the day of the test because you will need to exert yourself maximally if you are doing an exercise test. Bring busy material. You will have periods of waiting throughout the test so bring a book, newspaper, knitting or something. to keep you busy. No smoking four hours prior to the test. Smoking may interfere with the test results. (You shouldn’t be smoking anyway!) Wear a comfortable two-piece outfit and comfortable shoes. A hospital gown can be provided and men may be asked to take off their shirt. Slacks or shorts are preferred if you are exercising. You should wear comfortable footwear appropriate for brisk exercise if you are doing an exercise test. Do not wear oils or lotions before your test. Small sticky patches (electrodes) will need to stick to your chest. Your physician may also ask you to stop taking some of your heart medications on the day of your test. If you have any questions about your medications, ask your physician. Note: Do not discontinue any medication without first talking to our office. What happens during the test? When you enter the stress testing room, the technician will have you sign a consent form and will make sure you understand the test. A small IV will be started in a vein in your arm. Twelve electrode patches will be placed on your chest and torso. If you have hair on your chest, small areas may need to be shaved for the electrodes to adhere properly. The nuclear medicine tech will put your first injection of thallium through the IV. You will wait in the waiting room for at least 15 minutes to let the thallium circulate to your heart. Once your waiting period is over, the nuclear medicine tech will put you under the camera for about 15-20 minutes. You will lay on your back on a table with your hand behind your head. It is important for you to remain very still while the images are being taken. The camera will move about you. Following the completion of this first scan, you will be escorted to a stress testing room. The technician will have you lay on a stretcher while he/she hooks you up to equipment. Wires will be attached to the electrodes in order to monitor your heart rate and EKG. A resting EKG and blood pressure are recorded. Once the physician, PA or nurse practitioner arrives in the room, your test will begin.